1. Field of the Invention
The present invention relates to a temperature sensor.
2. Description of Related Art
Various apparatuses including automobiles are provided with temperature sensors as described in Japanese Patent Application Laid-open No. 2011-232066. The temperature sensor described in this patent document includes a thermistor element, a tablet, and a glass sealing part covering the thermistor element. The glass sealing part includes a body section located adjacent to the distal end surface of the tablet, and a head section that covers the thermistor element. The external shape of the glass sealing part is widest at a position on a cross-section that crosses the thermistor element in the head section. The body section is formed with a constriction at which the outer diameter thereof is minimum. Accordingly, the thickness of the glass sealing part is larger at its portion covering the periphery of the thermistor element than at the other portions thereof.
However, the above temperature sensor described in the above patent document has a problem as described below. The temperature sensor is used for a hydrogen tank of a fuel cell vehicle, for example, to detect the temperature in the hydrogen tank, a filling rate of hydrogen into the hydrogen tank being controlled based on the detected temperature. Shock and high pressures occur in the hydrogen tank at the time of filling hydrogen into the hydrogen tank. Accordingly, the thickness of the glass sealing part has to be increased at the head section and the body section including the constriction. However, if the amount of material for forming the glass sealing part is excessively increased to increase the thickness, it is likely that formation failure occurs in the glass sealing part, as a result of which the yield and productivity are lowered. Incidentally, the same problem occurs for uses other than hydrogen tanks, which require high resistivity to pressure, thermal shock and vibration.